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Thanks for reporting, I'll look into this issue after I fix issue <a class="issue-link

Hi @enricostara I get a new error when I add a second component `B` about dominion-ecs-java HOT 3 CLOSED

endison1986 commented on June 3, 2024

Hi @enricostara I get a new error when I add a second component `B`

from dominion-ecs-java.

Comments (3)

endison1986 commented on June 3, 2024

About this issue, I analysis source code, and found that the problem might be here.
dev.dominion.ecs.engine.system.ClassIndex.java

public IndexKey getIndexKey(Object[] objects) {
    int length = objects.length;
    boolean[] checkArray = new boolean[index + length + 1];
    int min = Integer.MAX_VALUE, max = 0;
    for (int i = 0; i < length; i++) {
        int value = getIndex(objects[i].getClass());
        value = value == 0 ? getIndexOrAddClass(objects[i].getClass()) : value;
        if (checkArray[value]) {
            throw new IllegalArgumentException("Duplicate object types are not allowed");
        }
        checkArray[value] = true;
        min = Math.min(value, min);
        max = Math.max(value, max);
    }
    return new IndexKey(checkArray, min, max, length);
}

under lines has concurrency problem.

int value = getIndex(objects[i].getClass());
value = value == 0 ? getIndexOrAddClass(objects[i].getClass()) : value;

If I createEntity in multiple threads, getIndex method will be called by multiple thread with result in zero. Also the getIndexOrAddClass method will be called multiple times. So I add a synchronized block to fix this issue temporary, Hope you have better way.

private final Object lock = new Object();
@SuppressWarnings("ForLoopReplaceableByForEach")
public IndexKey getIndexKey(Object[] objects) {
    int length = objects.length;
    boolean[] checkArray = new boolean[index + length + 1];
    int min = Integer.MAX_VALUE, max = 0;
    for (int i = 0; i < length; i++) {
        var componentClass = objects[i].getClass();
        var value = getIndex(componentClass);
        if (value == 0) {
            synchronized (lock) {
                value = getIndex(componentClass);
                if (value == 0) {
                    value = getIndexOrAddClass(componentClass);
                }
            }
        }
        if (checkArray[value]) {
            throw new IllegalArgumentException("Duplicate object types are not allowed");
        }
        checkArray[value] = true;
        min = Math.min(value, min);
        max = Math.max(value, max);
    }
    return new IndexKey(checkArray, min, max, length);
}